The overall objective of the proposed research is to evaluate the possible participation of calcium ion as an itnracellular messenger mediating hormone action on adipose tissue cells. Earlier studies using fat cells and other cell systems have provided data suggesting an action of calcium prior to and also antecedent to formation of cyclic AMP. In my laboratory, experiments to localize the site of calcium action on isolated fat cells are conducted by measuring cyclic AMP levels, rates of lipolysis and activity of the cyclic AMP dependent protein kinase in hamster adipocytes exposed to various stimuli and inhibitors of lipolysis. Subsequent studies will employ various pharmacologic agents which either promote (A23187 and X537A) or retard (verapamil and D600) calcium entry into cells. During the forthcoming year we shall continue our studies on hamster fat cells. Adipocytes from hamsters respond to alpha adrenergic agents with a partial inhibition of lipolysis and of cyclic AMP accumulation. We shall be looking at the interrelationships between calcium ion and alpha adrenergic control of lipolysis and cyclic AMP levels in fat cells from this species.